1. Field of the Invention
The present invention concerns a method for producing a time-limited image of a moving organ of a human or animal body, such as for imaging a beating heart, of the type wherein image data are acquired using an imaging apparatus, wherein using a sensor situated outside the body, a signal is registered that represents the movement of the organ that is to be imaged, and wherein the image data acquisition is coordinated with this signal. The present invention also concerns a sensor for use in such a method, as well as a system, having such a sensor, for producing time-limited image of a moving organ of a human or animal body. The present invention also concerns a method and a device for displaying images obtained using such a method.
2. Description of the Prior Art
In modern medicine, many types of imaging modalities are known, the basic goal of which is to obtain comprehensive knowledge of a particular organ and its state without having to surgically open the body. Typical medical imaging systems include, for example, magnetic resonance systems, computed tomography systems, x-ray systems, and ultrasound systems. Such medical imaging systems are used, for example to obtain images of bone structure, the brain, the heart, the lungs, the gastrointestinal region, etc. When recording images of an organ that moves, for example cardiological images, images of the lungs, or images of the peristaltic action of the small intestine or the swallowing process of the esophagus, it is often desirable to produce an image at a particular point in time (static image) or within a particular time period of the movement, in order to observe the behavior of the organ precisely at this point in time or during this particular time period.
One known method for this purpose is gating. In this method in the case of cardiological imaging as an example, an ECG signal is recorded. From the ECG, a particular significant event, for example the occurrence of the R-peak of the ECG, is used as a trigger signal for making an exposure at a precisely determined point in the movement of the heart. A problem with triggering with the aid of an ECG is that for this purpose a number of electrodes must be attached directly to the body. These electrodes are electrically conductive sensors, generally made of metal, which can cause disturbances in the recorded images. In addition, it takes a certain amount of time to attach all the required electrodes to the skin of the person or animal being examined. While the patient or animal is being connected to the ECG apparatus, the imaging system generally cannot be used for other purposes. This additional waiting period, taking place for a large number of examinations, unnecessarily reduces the active use of the relatively expensive imaging systems, and thus increases the costs of an individual examination.
In order to solve the problem of the sensor causing disturbances in the recorded images of the organ, in U.S. Published Application 2004/0111025, it is proposed to situate a suitable sensor outside the measurement space of the imaging system and to connect the sensor to the patient via a patient-sensor interface. In the publication, the use of a liquid-filled non-metallic conductor tube in combination with a mechanical sensor is described, for example an acceleration sensor, that reacts to non-electrical events in the body, such as breathing. The patient-side of the patient-sensor interface must be secured on the thorax of the patient. Movement due to the patient's breathing is then communicated to the sensor via the liquid-filled conductor tube. There the signal is picked-up by the sensor. The signal obtained with this additional sensor is then used to control the image data acquisition such that images of the organ, in particular states of movement, are produced. As long as the sensor does not interfere with the imaging, the acceleration sensor can be positioned directly on the patient. In imaging modalities in which this would result in a superimposition of the sensor in the imaging exposures, the patient-sensor interface must be intermediately coupled, which is relatively difficult. For this reason, using this method it is not possible to rapidly prepare the patient for an examination by the imaging system.